SRAMs may be arranged in a domino-logic structure in which two or more SRAM cells are connected in parallel to two local bit lines. One of the two local bit lines is coupled to a global bit line through a global bit line discharge logic. Both the local and global bit lines in a domino SRAM are precharged high before a read operation, and may be discharged, or “pulled down” to ground during a read operation. A particular cell is selected for reading by activating the cell's word line. One of the two precharged local bit lines coupled to the selected cell is discharged during a read operation. If the discharged local bit line is the one that is coupled to the global bit line, the discharge of the local bit line activates logic that discharges the global bit line.
FIG. 1 is a schematic representation of a portion of a prior art SRAM circuit 100 having a column of SRAM cells 110, a global bit line (GBL) 106, a local eval logic 122, and a GBL discharge logic 120. Each SRAM cell 110 includes a pair of cross-coupled inverters, 130, 132. SRAM cells are connected to the local eval logic through a local bit line true (LBLT) 102 and a local bit line complement (LBLC) 104. The LBLT and the LBLC are precharged by a local bit line precharge line (LBL_PCH) 114 and transistors 1P1 and 1P2. A write true line (WT) 126 and its associated transistors 1N3 and 1N6, a write complement line (WC) 124 and its associated transistors 1N4 and 1N5, and a write enable line (WE) 118 and its associated transistor 1N7 control the write operations of the cell 110. The GBL 106 is precharged by a GBL precharge line (GBL_PCH) 112 and a transistor 1P3.
A read operation employs the GBL discharge logic 120. As an illustration, to read a “one” from the cell 110 in the SRAM column, a word line (WL) 108 turns on pass transistors 1N1 and 1N2. When the “one” is read, the LBLT 102 remains high while the LBLC 104 is pulled down. The value on the LBLC is inverted to a “one” by an inverter 116, which turns on an N-channel field-effect (NFET) transistor 1N8. Transistor 1N8 pulls down the precharged GBL 106 to ground, effectively placing an inversion of the “one” on the GBL.